Background information on technology and terms can be found in the IEEE 802 and ITU-T G.984 standards. Rising energy costs, the increasing size of data centers, and the increasing density of electronic equipment are some of the reasons why businesses have become increasingly sensitive to the impact of energy consumption in operations. In particular, many companies are looking at information technology (IT) systems' power usage to determine whether the energy costs can be reduced. One aspect of power usage is energy consumption by communications equipment.
IEEE 802-style networks (which in the context of this document generally includes and ITU-T G.984-style networks) are a popular choice for both enterprise and first-mile access communications. One example of an IEEE 802-style network is the Ethernet networking standard, implemented in such standards as 100 Base-T, 10 GBASE-R, and Ethernet passive optical networks (EPONs). The importance of power saving in IEEE 802-style networks can be seen from the IEEE 802.3 Working Group that has recently formed an Energy-Efficient Ethernet (EEE) Task Force, officially named 802.3az, to define a solution for reducing the average power consumption of copper Ethernet. A variety of conventional solutions has been proposed.
U.S. patent application Ser. No. 60/172,986 to Linghsiao Wang and James Yik for Power Saving For Ethernet MAC Control Logic teaches a method to control power within a communications device by stopping and starting the clock signals between the MAC control logic module and the frame processor module.
U.S. patent application Ser. No. 20090204828 to Wael William Diab, et al for Hybrid Technique in Energy Efficient Ethernet Physical Layer Devices teaches a hybrid approach that combines and manages multiple low power modes. The hybrid approach uses a combination of a low power idle technique and a physical interface technique that can be selectively activated within a communications device. In the physical interface technique, a link uses can use a high data rate when data transmission needs are high, and can use a low data rate when data transmission needs are low. In the low power idle technique, the transmitting side of the link can be designed to enter into a low power idle mode where the bulk of the physical interface and the energy on the link is turned off (put to sleep) when there is no data transmission. The transmitting physical interface is not turned completely off, rather the transmitting physical interface sends refresh signals to enable the receiver to maintain link synchronization and receive advance notice of wakeup from the low-power mode.
U.S. patent application Ser.No 20080304519 to David J. Koenen et al for Method for Ethernet Power Savings on Link Aggregated Groups teaches providing the ability to lower the power consumed by a group of Ethernet links when organized in a Link Aggregation Group. When the server or switch senses low bandwidth utilization across multiple links in the group, it will negotiate the transition of un-necessary links to a lower power state. When the bandwidth requirements increase, the algorithm will quickly re-establish links and distribute the Ethernet traffic across the multiple links when necessary.
U.S. patent application Ser. No 20090119524 to Robert Hays for Energy Efficient Ethernet Using Active/Idle Toggling teaches that an Ethernet controller may be configured to operate in an active power state to transmit or receive data packets at a maximum available link speed. Once the data packets are transmitted or received, the Ethernet controller may be configured to operate in an idle power state to reduce energy consumption. Hays defines the “idle power state” as a power state that is sufficient to maintain an open link with the link partner, but insufficient to transmit or receive data. In other words, the “idle power state maintains the Ethernet communications link between the Ethernet controller and the link partner.
In the context of this document, a user communications device, or more simply called a user device, refers to the equipment generally placed locally to a user, and provides a user with an interface for transmitting and receiving with an associated communications network (more simply called a network). In the context of this document, a network communications device, or more simply called a network device, refers to the equipment generally placed centrally to a plurality of users, operationally connected to user devices by a communications network, and provides an interface for transmitting and receiving with the associated communications network. A network device can provide communications between user devices on a network and/or communications between user devices and another network.
Conventional solutions for power saving in Ethernet networks focus on changing the data rate of the link or selectively lowering the power consumption of the physical (PHY) interface of a user device. While using a lower data rate to transmit data saves power over using a higher data rate, maintaining transmission at a lower data rate continues to use power. When transmitting via analog communications, for example copper Ethernet, the transmitter can transmit at lower power levels to reduce power, but the transmitter continues to use power. Controlling power within a user device by monitoring for idle transmission time and turning off the device's transmitter saves power for the transmitter, but the receiver continues to use power. The various conventional low power and idle states can save power for the transmitter and receiver, but still require power consumption in a user device to monitor the communications channel for a “wakeup” signal from a network device.
There is therefore a need for a system and method for power saving in networks in which the transmission medium does not facilitate receiver detection of a transmitter's signal that the transmitter is exiting low power state, including IEEE 802-style and ITU G.984-style networks including, but not limited to Ethernet networks. It is further desirable to use information from user and network devices for initiating power savings by the user device.